A large number of abdominal surgical procedures are performed with laparoscopic techniques in order to avoid a large skin incision. Typically in laparoscopic surgery, a special needle (e.g. a needle similar to the needles described in U.S. Pat. No. 4,808,168 and U.S. patent application Ser. No. 07/808,152) is inserted through the skin, and used to pressurize the abdominal cavity with an insufflating gas such as carbon dioxide (CO.sub.2). Once the abdomen is adequately dilated, the needle is removed and a rigid access tube or cannula with a diameter larger than the pneumoneedle (for example 5, 10 or 11 mm) is passed through the skin in generally the same location.
The cannula provides access for laparoscopic surgical tools or instruments such as a laparoscope, a stapler or a surgical clip applier. Examples of such surgical instruments are described in U.S. Pat. Nos. 5,040,715, 5,084,057, 5,100,420, 5,171,247, 5,171,249 and 5,176,695. To drive the access tube through the skin, the surgeon places a trocar in the lumen of the cannula to provide a sharp, leading edge for cutting tissue.
The art is replete with trocar and cannula assemblies, including those shown in U.S. Pat. Nos. 4,535,773, 4,601,710, 4,654,030, 4,902,280, 4,931,042, 5,104,382, 5,116,353 and 5,152,754. Existing trocar and cannula assemblies encounter problems because, after the cannula has been inserted into the abdominal cavity, the cannula tends to become displaced from the abdominal cavity (e.g. the cannula tends to become dislodged from the abdominal cavity) due to a variety of factors. Those factors include friction between the laparoscopic tool and the inner surfaces of the cannula which tend to provide a removal force on the cannula when the laparascopic tool is removed from the abdominal cavity (and cannula), and the frequent manipulation of laparoscopic instruments such as clip appliers and staplers within the cannula by the surgeon. Even an inadvertent jar of the cannula by medical personnel may dislodge the cannula from the abdominal cavity.
Obstacles associated with the surgical environment complicate the task for devices which are intended to retain the cannula within the abdominal cavity. The obstacles include friction reducing agents such as fluids and fat tissue which deleteriously affect parts which rely on friction, and adhesive contaminants such as blood and other liquids which may deleteriously affect an adhesive bond with the skin of a patient.
The art has diverse devices for addressing this problem. For example, U.S. Pat. No. 5,009,643 to Reich et al. and European Patent Application No. 0 494 520 disclose a cannula having anchoring threads. The cannula is screwed into the tissue of the abdominal wall and the anchoring threads hold the cannula in the abdominal cavity. Other, similar approaches include locating a member at the distal end of the cannula which expands once the cannula is within the abdominal cavity. See for example, U.S. Pat. No. 5,147,316 to Castillenti (balloon), and U.S. Pat. No. 5,122,122 to Allgood (mushroom hinged member). However, some persons in the surgical field hold these approaches in low regard due to the belief that they may unduly traumatize tissue.
Other approaches to this problem are shown in U.S. Pat. No. 5,073,169 to Raiken and U.S. Pat. No. 5,137,520 to Maxson et al. Those patents disclose a device having a hole through which the cannula is threaded. Generally, the hole is sized to form a tight friction fit between the device and the cannula. The device is also adhesively adhered to the skin of a patient.
The Origin Trocar Gripper.TM. has been on sale in this country by Origin Medsystems, Inc. prior to the filing date of the present application. The Origin Trocar Gripper.TM. comprises a generally flat patch with an aperture through which the cannula is threaded. The aperture is sized for a friction fit between the cannula and the patch. The friction fit assists in holding the cannula within the abdominal cavity. However, the friction reducing agents mentioned above may adversely affect the performance of this device.